package com.ayoka.widget;

import android.support.v4.view.ViewPager;
import android.view.View;

/**
 * Created by jinchunping on 2018/3/7.
 */

public class ScaleTransformer implements ViewPager.PageTransformer {
    private static final float MIN_SCALE = 0.9f;
    private static final float MIN_ALPHA = 0.9f;
    private static final float MAX_SCALE = 0.1f;

    @Override
    public void transformPage(View page, float position) {
        if (position < -1 || position > 1) {
            page.setAlpha(MIN_ALPHA);
            page.setScaleX(MIN_SCALE);
            page.setScaleY(MIN_SCALE);
        } else if (position <= 1) { // [-1,1]
            float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            if (position < 0) {
                float scale = 1 + MAX_SCALE * position;
                page.setScaleX(scale);
                page.setScaleY(scale);
            } else {
                float scale = 1 - MAX_SCALE * position;
                page.setScaleX(scale);
                page.setScaleY(scale);
            }
            page.setAlpha(MIN_ALPHA + (scaleFactor - MIN_SCALE) / (1 - MIN_SCALE) * (1 - MIN_ALPHA));
        }
    }
}
